Numerous conventional sensors can detect at least one rotation characteristic of rotating elements. Rotation characteristics are to be understood in general as characteristics which at least partially describe the rotation of the rotating element. These may be, for example, angular velocities, rotational speeds, angular accelerations, rotation angles, angle positions, or other properties in this case, which may characterize a continuous or discontinuous, uniform or nonuniform rotation of the rotating element. Examples of such sensors are described in Konrad Reif (editor): Sensoren im Kraftfahrzeug [sensors in motor vehicles], first edition, 2010, pages 63-73 and 120-129.
German Patent Application No. DE 10 2012 221 327 A1 describes a speed sensor, which has at least one magnetic sensor, to enable a detection of the events generated by magnetic event timers of a first reading track in at least one first speed range of a rotating element and to enable a detection of the magnetic events generated by magnetic event timers of a second reading track in at least one second speed range, which is different from the first speed range, a number of the magnetic event timers of the second reading track exceeding a number of the magnetic event timers of the first reading track by at least a factor of 1.4.
A particular focal point of the present invention, to which the present invention is basically not restricted, however, is the detection of an absolute angle position of a camshaft. Camshaft sensors are typically used for synchronization between camshaft and crankshaft during an engine start. Crankshaft and camshaft are each equipped with a sensor wheel. For the camshaft, a tooth-gap pair on the sensor wheel is normally used for each cylinder. Accordingly, a four-cylinder engine has a sensor wheel including four tooth-gap pairs on the camshaft. Sensors which are based on the Hall effect or an XMR principle (X-magnetoresistive) are used for the measurement. A permanent magnet is typically installed in these sensors, whose magnetic field is modulated by the rotating sensor wheel. This modulated magnetic field may be detected with the aid of the mentioned principles and therefore converted into a usable signal. The camshaft sensor is used for the coarse detection of the engine cycle or the determination of which engine cycle the engine is in, i.e., the cylinder position. The sensors may have a function for the unambiguous detection of a tooth or a gap. The sensors may also have a function in which the sensor may be pivoted in relation to the running direction of the sensor wheel, without the sensor signal being interrupted. All sensors detect the tooth edges of the sensor wheel teeth.
In spite of the improvements caused by these sensors, there is still potential for improvement. Thus, the dynamically adjustable camshaft positions of the most recent engine generations require a high-resolution detection of the camshaft position. In addition, it is necessary to detect this camshaft position as an absolute angle. The previous sensors are not capable of meeting these requirements. An absolute angle may only be computed by the engine control unit in the dynamic case, i.e., with a rotating sensor wheel, and only coarsely on the basis of the tooth-gap combination. The sensor signal alone cannot supply an absolute angle. The resolution is also limited by the small diameter of the sensor wheels used. Minimal gap sizes, which have to be maintained, result due to these small diameters.